Process for upgrading residua



958 A. 4VOORHIES, JR 2,

PROCESS FOR UPGRADING RESIDUA United States Patent PROCESS FOR UPGRADINGRESIDUA Alexis Voorhies, Jr., Baton Rouge, La., assignor to 'EssoResearch and Engineering Company, a corporation of Delaware ApplicationNovember 23, 1953, Serial No. 393,617

3 Claims. (Cl. 208-56) The present invention relates to an improvedprocess for converting residua such as the heavy residuum resulting fromrefining of petroleum and analogous material. The feed stock may be apetroleum residuum of high boiling range or it may be a total crude ofthe same general characteristics. Coal tar, shale oil and the like orthe heavy ends thereof may be used as the feed.

In the prior art numerous proposals have been made for converting heavyresidual oils to more volatile and more valuable products. As a rule,these heavy feed stocks have been converted by coking, that is, bysubjecting them to high temperature treatment for a suificient period oftime to crack part of the feed to lighter products and to degrade aportion to coke with the accompanying production of gas. The gas andcoke so produced are normally of less value than the motor fuel and gasoil products. It is therefore preferred to produce as much motor fueland gas oil as possible with a minimum conversion to gas and coke. Anobject of the present invention is to accomplish such conversion.

It has also been proposed recently to convert heavy residual oils of thetype mentioned above by the use of a hydrogen donor diluent. The feedand the diluent are subjected to mild thermal treatment which results incracking the feed to obtain a good distribution of products. Thisprocess has been called for brevity the hydrogen donor diluent crackingprocess or more briefly the HDDC process. The present invention involvesa specific improvement in the HDDC process.

According to the present invention a suitable feed stock such as heavypetroleum residuum is combined with a hydrogen donor diluent, to bedescribed, and the mixture is preheated to a suitable temperature,usually between about 750 and 1000 F. A preferred temperature is betweenabout 800 and 900 F. The mixture is passed into a reactor where theingredients remain for a time and at a temperature suitable foraccomplishing the hydrogen donor diluent cracking. This cracking resultsin the production of substantial proportions of gasoline, of light gasoil boiling between about 430 and 700 F., of heavy gas oil boilingbetween about 700 and 1050 F., and a bottoms fraction boiling aboveabout 1050 F. The motor fuel and light gas oil products are taken tostorage or to further processing such as hydroforming or catalyticcracking. A portion of the 700 to 1050 F heavy gas oil fraction also maybe taken to a catalytic cracking operation. Part of the same fraction istreated according to the present invention, to convert it substantiallyto armatic products for a purpose to be described. The remainder of the700 to 1050 F. fraction is passed through a hydrogenator.

The portion of the heavy gas oil which is treated to convert it to asubstantial degree to aromatics is contacted with a suitable catalystfor this purpose. A highly satisfactory process for aromatizing involvesan operation in the nature of hydrocracking wherein a suitable catalystis used and hydrogen gas is evolved. Such hydrocracking processespreferably use a chromia alumina catalyst and are operated at a pressureof 50 to 500 p. s. i. g. and at a temperature between about 900 to 1050F. with a feed rate of 0.6 to 0.9 w./-hr./w. for a fixed or fluid bedprocess. A suitable catalyst consists of 95% of alumina and 5% ofchromia.

Typical data from an aromatizing process are listed below in Table I.

Table I East Texas Wide Out West Texas Operating Conditions Light GasParaflinic Wide Cut Oil Gas Oil Gas Oil Reactor Temperature, "F 975 975975 Reactor Pressure p. s. i. g 100 Feed Rate, W./ W 0.72 0.72 0.72Hydrogen Rate, 0. F./B 3, 000-5, 000 3, 000-5, 000 3, 0005, 000 400F.+Gas Oil, V01. Percent on e 31 34 Gravity, API 14. 4 15. 4 15. 3Aniline Point, F 34 52 54 Feed Stock Inspections:

Gravity, API 33. 7 30. 3 29. 2 Aniline Point, "F 172 192 165 Theproducts from the aromatizing, or more specifically hydrocracking,process described contain considerable proportions of condensed ringaromatics which are excellent hydrogen donor materials when partiallyhydrogenated. The decrease in the aniline point indicates tungstensulfide.

the increase in aromatics. The aromatization product contains 65 topercent of aromatic hydrocarbons of which about one-half are of thedesired bicyclic or higher condensed ring type. The products from thearomatizer are fractionated into the same cuts, temperature-wise, as theproducts mentioned above. Thus products boiling in the gasoline rangemay be added to the gasoline product from the first reactor and thelight gas oil may be added to the primary light gas oil.

The 700 to 1050 F. aromatized product is passed to a hydrogenator alongwith a portion of the original heavy gas oil (700 to 1050 F. cut)mentioned above. These combined materials are hydrogenated partially but.not completely by treatment with 200 to 2000 s. c. f. of hydrogen perbarrel of feed to the hydrogenator. The precise method of hydrogenatingforms no part of the present invention but a suitable process involvesthe use of a standard hydrogenating catalyst, preferably of the sulfurinsensitive type, e. g. molybdenum sulfide, or nickel- Hydrogenation iscarried out at moderate temperatures (600-800" F.) and at suitablepressure such as 200 to 1000 pounds per square inch.

It will be understood that the purpose of the aromatizing step is toprovide continuously a make-up stream of the most desirable type ofaromatics. Such a make-up stream is necessary because the hydrogen donorreaction is not completely selective and the distillation of products inthe primary fractionator is not completely selective. Otherwise thedesired condensed ring products would circulate indefinitely Within thesystem, picking up hydrogen in the hydrogenator and releasing it in theHDDC reactor. However, a small proportion of the total recycle throughthe hydrogenator is sufiicient to keep the system in balance. Thus 5 to10% of the heavy gas oil fraction, 700 to 1050 F., may be passed throughthe aromatizer and the 700 to 1050 F. fraction of the aromatizedproduct, which may amount to only about half the feed to thearor'natizer, is combined with the bulk of the heavy gas oil forhydrogenating and recycling to the HDDC reactor.

In a typical example, l0,000B./D. of residuum feed are mixed with 20,000B./D. of a recycle stream, and after suitable preheating the mixture iscontacted in the reactor at 800-900 F. and at a pressure that may bevaried from substantially atmospheric to 500 p. s. i. g., and

higher. The recycle stream contains the hydrogen donor as will bedescribed subsequently. The converted products pass from the reactor toa still where conventional separation is made to (give gas, gasoline, a430-700 F. cut, a 7001050 F. cut, and .a 1050 F.+ bottoms. The 700-l050F. cut is split into two streams. The larger stream consisting of 14,500B./D. is sent to a low pressure hydrogenation step before recycling tothe reactor. The smaller stream of 700-l050 F. material comprising 1000B./ D. is sent to the aromatizer for the purpose of producing a 7001050F. cut consisting to a large extent of polycyclic, condensed ringaromatics. The product from the aromatizer goes to a small still wherethe products are separated into gas, gasoline, a 430-700" F. cut, a700-1050 F. material, and 1050 F.+ bottoms. The small amount of 1050 F.+bottoms is mixed with the 500 B./D. of 1050 F.+ material from theprimary still and is included in the 20,000 B./'D. of recycle materialwhich enters the process. The highly aromatic 700-1050 F. cut consistingof 500 B./D. is blended with the 14,500 B./D. of primary 7501050 F. cutpreviously mentioned, and this combined feed of 15,000 B./D. goes to thehydrogenation step.

The invention will be more clearly understood by reference to theattached drawings which illustrate diagrammatically two preferredembodiments thereof. Figure 1 shows schematically a system incorporatingthe features mentioned above and Figure 2 shows an alternative andsomewhat simplified system.

Referring first to Figure 1 the feed, a suitable petroleum residuum forexample, enters through line 11 and passes through a suitable heater,for example, a coil 13 where its temperature is raised to between 750and 1000 F. A preferred temperature is between 800 and 900 F. A recyclestock described below is preheated simultaneously and the combinedproducts are passed through line 15 into the HDDC reactor vessel 17. Inthis vessel the reaction is allowed to continue for a suitable period oftime which may range from A to 4 hours or more. The products fromreactor 17 pass through line 19 to a fractionator or a distillation unit21. Here the C and lighter gases are taken overhead through line 23. Amotor fuel fraction from C to about 430 F. passes out through line 25.The 430 to 700 F. light gas oil passes off through line 27 and the 700'to 1050 F. heavy gas oil through line 29. A bottoms fraction passesthrough line 31 to return lines 57 and 33 which recycle it to the heater13.

The heavy gas oil fraction is divided approximately into two or moreparts depending upon the product distribution desired. Thus a portionmay be taken through line 35 as a product for direct use or for feedstock to a catalytic cracker. A minor portion, for example 5 to is ledthrough line 29 to an aromatizing zone 39. A major fraction is carriedthrough line 41 to pass through the hydrogenator and recycle with thefeed as will be described.

The fraction passed to the aromatizer is treated with a suitablearomatizing catalyst at a temperature between 900 and 1050 F. underpressure which may be between 50 and 500 p. s. i. g. The products fromthe aromatizer are taken to a fractionator 43 through line 45. Here agas fraction which may include hydrogen is carried overhead through line47 to combine with the gas in line 23. When this gas is rich inhydrogen, as it is in some cases, the hydrogen may be returned to thehydrogenator described below. The products from fractionator 43 whichboil in the motor fuel range are taken off through line 49 and the lightgas oil through line 51 to combine respectively with the products inlines 25 and 27.

The 700 to 1050 F. fraction from the fractionator 43 is passed through aline 53 to the hydrogenator 55. A bottoms fraction from fractionator 43is taken through line 57 to recycle with the bottoms from fractionator21 to line 33.

The aromatized heavy gas oil fraction is combined with the heavy gas oilfrom line 41 and by line 53 is transferred to the hydrogenating unit 55.This contains a suitable hydrogenating catalyst such as molybdenumsulfide or other suitable catalyst of known type. Hydrogen gas, or amixture rich in hydrogen, is supplied through line 61 to thehydrogenator, spent gas being taken off overhead in line 63 through asuitable valve 65. It may be and frequently is desirable -to recycle thespent gas from line 63 to the hydrogen feed line 61 to conservehydrogen.

The hydrogenator 55 is operated under such conditions as to partiallybut not fully hydrogenate the condensed ring aromatic constituentsentering through line 53. As noted above these constituents areconsiderably enriched by passing part of the hydrogenator feed throughthe aromatizing operation at 39.

The hydrogenated material is taken from hydrogenator 55 through line 67to combine with the refluxing bottoms from the fractionators. Thesecombined materials are added to the feed and passed through the heater13 to the HDDC reactor where the cycle is repeated. With an averagepetroleum residuum feed stock and with the various streams divided inthe proportions suggested above, the process of this invention may yieldabout 5% by volume of gasoline, 20% of 400 to 700 F. light gas oil and70% of 700 to 1050 F. heavy gas oil per pass. The overall efficiencywill vary with the division of the 700 to 1050 F. stream from line 29.These yields are merely illustrative and will vary to some extent withthe quality of the original feed stock. In general conversion ofapproximately may be expected. By recycling, the bottoms may be treatedto extinction. Gas yields are relatively low.

Referring now to Figure 2 the same general process is shown except thatthe effluent from the aromatizer is recycled to the primaryfractionator. This eliminates the need for a secondary fractionator 43as shown in Figure 1.

Briefly, feed enters through line 71 to heater 73 and HHDC reactor 75.The reaction products are taken to fractionator 77 through line 79. Thegas, gasoline, light gas oil, and heavy gas oil are taken offrespectively through lines 81, 83, 85, and 93. Bottoms from fractionator77 are recycled through line 89 to return line 91.

A portion of the 700 to 1050 F. heavy gas oil passes directly throughline 93 to the aromatizer 95 from which the total products are recycledthrough line 97 to the fractionator 77. The remainder of the 700 to 1050F. gas oil is taken to the hydrogenator 99 through line 101 except thata portion may be withdrawn as product through line 103 if desired. Ifwill be understood that in all these lines, and in the lines of Figure 1suitable valves will be provided as needed.

The heavy gas oil taken to the hydrogenator 99 through line 101 includesan aromatized portion recycled through the fractionator. This material,together with gas oil which has not been aromatized, is partiallyhydrogenated, hydrogen being supplied through a line 105 and spent gasremoved through a line 107 as in Figure 1.

The partially hydrogenated feed is recycled through line 109 to combinewith the fractionator bottoms in line 91 and both are taken through theheater with the fresh feed to the HDDC reactor.

It will be understood that various modifications may be made in thearrangement and use of the systems described in detail above withoutdeparting from the spirit of the invention.

What is claimed is:

1. The process of upgrading heavy oil to produce lower boiling productswhich comprises combining with one volume of feed one to four volumes ofa partially hydrogenated recycle stock obtained as describedhereinafter, heating the combined feed and recycle stock to atemperature within the range of 750 to 1000 F., passthe heated mixtureinto a reaction zone and reacting for a suflicient time to transferhydrogen from the recycle stock to the feed and to crack the mixture,fractionating the products of the reactor to obtain a motor fuelfraction, a light gas oil fraction and a heavy gas oil fraction,aromatizing part of said last mentioned fraction, partiallyhydrogenating the aromatized and unaromatized portions of said heavy gasoil fraction and recycling the partially hydrogenated fraction to thefeed.

2. Process according to claim 1 wherein the feed and recycle stock arepreheated to a temperature between 800 and 900 F.

3. The process of converting heavy residual oil to products of motorfuel and gas oil boiling range which comprises: combining with onevolume of feed one to four volumes of a partially hydrogenated recyclestock obtained as described hereinafter, heating the combined feed andrecycle stock to a temperature between about 750 to 1000 F., andreacting this mixture for a period of about M4 to 4 hours to transferhydrogen and cause hydrogen donor diluent cracking of the feed,fractionating the cracked products to separate therefrom a heavy gas oilfraction boiling within the range of about 700 to 1050 F., aromatizingabout 5 to 10% of said heavy gas oil and fractionating the aromatizedproduct, segregating a first fraction of the aromatized product boilingabove about 1050 F. and recycling it to the said reaction zone,segregating a second fraction of the aromatized product boiling in therange of about 750 'to 1050" F. and combining said second fraction withat least a part of the non-aromatized heavy gas oil, partiallyhydrogenating said combined heavy gas oils, and recycling them to thereaction zone.

References Cited in the file of this patent UNITED STATES PATENTS2,249,337 Visser July 15, 1941 2,290,033 Burk et al July 14, 19422,426,929 Greensfelder Sept. 2, 1947 OTHER REFERENCES Sachanen: ChemicalConstituents of Petroleum (1945), page 223, Reinhold Publishing Corp.

1. THE PROCESS OF UPGRADNG HEAVY OIL TO PRODUCE LOWER BOILING PRODUCTSWHICH COMPRISE COMBINING WITH ONE VOLUME OF FEED ONE TO FOUR VOLUMES OFA PARTIALLY HYDROGENATED RECYCLE STOCK OBTAINED AS DESCRIBEDHEREINAFTER, HEATING THE COMBINED FEED AND RECYCLE STOCK TO ATEMPERATURE WITHIN THE RANGE OF 750* TO 100*F., PASSTHE HEATED MIXTUREINTO A REACTION ZONE AND REACTING FOR A SUFFICIENT TIME TO TRANSFERHYDROGEN FROM THE RECYCLE STOCK TO FEED AND TO CRACK THE MISTURE,FRACTIONING THE PRODUCTS OF THE REACTOR TO OBTAIN A MOTOR FUEL FRACTION,A LIGHT GAS OIL FRACTION AND A HEAVY GAS OIL FRACTION, AROMATIZING PARTOF SAID LAST MENTIONED FRACTION, PARTIALLY HYDROGENATING THE AROMATIZEDAND UNAROMATIZED